The upper right flipper stopped working after a wire came off one coil lug and touched the other lug. Once the wire is fixed, the bat goes up on its own as soon as the coin door is closed (flipper power on) and stays up until the fuse blows.
Upper right flipper locks up and blows its fuse after a loose coil wire: shorted MOSFET
Cause: The short across the coil damaged the flipper's drive MOSFET on the driver board, which now fails shorted and holds the coil on.
Checks
- Note whether the bat goes up by itself before the fuse blows: that points to a shorted driver rather than a shorted coil.
- With power off, test the flipper's drive transistor on the driver board with a meter's diode test.
Fix
- Replace the shorted MOSFET for that flipper on the driver board.
- Check the coil and its diode as well, and refit the coil wire firmly.
- Take care when desoldering: pulling out a through-hole plating needs a wire repair through the board.
Systems
Games
Related tips
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Source: Pinball Repair help group!! (Facebook group)